Method for forming a serrated tearing edge with a hardened thermoplastic resin layer



July 11, 1967 s REILLY 3,330,685

J. METHOD FOR FORMING A SERRATED TEARING EDGE WIT A HARDENED THERMOPLASTIC RESIN LAYER Original Filed Nov. 14, 1962 H I I; Q l

Inventor 7 John S Rail w [4 Byhis flzi'orney Mh lg C United States Patent METHOD FDR FORMING A SERRATED TEARING EDGE WITH A HARDENED THERMOPLASTI RESIN LAYER John S. Reilly, Beverly, Mass, assignor to United Shoe Machinery Corporation, Flemington, NJ. and Boston, Mass, a corporation of New Jersey Original application Nov. 14, 1962, Ser. No. 237,648, now Patent No. 3,169,685, dated Feb. 16, 1965. Divided and this application Nov. 25, 1964, Ser. No. 413,822

4 Claims. (Cl. 117-44) This case is a division of my copending application Ser. No. 237,648, filed Nov. 14, 1962 entitled Serrated Tearing Edges. The application has issued as U.S. Patent No. 3,169,685, on Feb. 16, 1965.

This invention relates to an improved method of making serrated edge portions for tearing sheet material and particularly to a method of making such an edge to serve as a sheet severing portion of a dispensing carton for a roll of sheet material.

Dispensing cartons for rolled sheet material such as wax paper or aluminum foil are commonly provided with a cutting edge alfixed to a wall of the carton for severing desired lengths of the sheet material. In the past these cutting edges have been strips of metal serrated along the exposed edge and stapled or otherwise fixed to the carton wall. Metal strips have sharp corners or edges which may inflict cuts and scratches in handling the carton. Also such metal strips are relatively expensive.

It has been proposed to eliminate these difilculties by impregnating an edge portion of a fibrous carton blank with a hardening agent and to serrate the edge. This hardened and serrated edge then constitutes a tearing edge portion integral with the carton. However, it has not been practical under usable manufacturing procedures to impregnate the hardening agent through the thickness of the carton material or to associate such material in a manner to secure efiective cooperation of the hardening agent and carton material. Previous cutting edges have tended to lose their ability to tear cleanly after very little use because of blunting or distortion of the serrations by the sheet material.

It is an object of the present invention to provide a simplified and rapid method for forming an improved serrated edge portion for tearing sheet material where the teeth constituting the serration retain a superior tearing ability on extended use.

To these ends and in accordance with the present invention a hard tearing edge and cooperative integral stiffening reinforcement is formed on marginal face and serrated edge surface portions of a fibrous sheet. Hard resinous material is deposited to form the novel edge and reinforce ment by pressing marginal face portions of a fibrous sheet adjacent a serrated edge into a thin molten layer of resinous material on a hot carrier surface. The sheet diplaces portions of the molten layer and causes it to deposit on desired portions of the face and edge of the sheet. After removal of the sheet from the molten layer the material deposited hardens to form a superior reinforced tearing edge firmly associated with the sheet.

The invention will be described further in conjunction with the accompanying drawings forming part of the disclosure in which:

FIG. 1 is a plan view of a section of sheet material showing resin deposited on the face and serrated edge portions of a sheet to provide a reinforced tearing edge;

FIG. 2 is a cross section taken on the line II-II of FIG. 1 and on an enlarged scale showing the relation of the deposited resin on the face and serrated edge surface portions of a sheet material;

FIG. 3 is a diagrammatic elevational view illustrating an arrangement of apparatus through which serrated edge sheet material may be passed to form the reinforced edges;

FIG. 4 is a partial elevational view at right angles to the direction of FIG. 3 and on a larger scale, showing the relation of certain parts of the apparatus of FIG. 3 with serrated edge sheet material being brought into association with molten resinous material;

FIG. 5 is a fractional view on an enlarged scale showing the application of molten resinous material to a serrated edges sheet in accordance with one form of the present invention;

FIG. 6 is a fractional view on an enlarged scale showing the application of molten resinous material to a serrated edge sheet in accordance with another form of the present invention; and

FIG. 7 is an enlarged view of 1a serrated edge sheet and reinforcing resinous material on its face and edge surface portions as formed according to the procedure shown in FIG. 6.

In the present tearing edge, relatively thick deposits 10 of hard resinous material on the edge portions 12 of the teeth 14 constituting serrations of a fibrous sheet 16, e.g. a cardboard carton blank, provide points which aid in tearing sheet material. The teeth 14 should be at least about inch in height and have a pitch of at least inch. A film 18 of hard resinous material integral with the deposits 10 and extending along marginal portions of the surface of one face 20 of the sheet 16 from the points of the teeth 14 to a line at least about V inch below the. bottom of the teeth serves to unify the deposits 10 into an effective tearing edge. The film 18 may be as little as 0.002 inch in thickness. The deposits 10 on the edge portions of the teeth 14 and the film 18 conform to and are in intimate adhering engagement with the fibrous sheet 16 so that the film 18 and edge deposits 10 form with the fibrous sheet 16 beam structures for the teeth 14 which are strongly resistant to bending. The fibrous sheet 16 may be any of the usual carton materials such as cardboard, chipboard, sulfite board and the like and will ordinarily be from about 0.015 to about 0.02 inch or more in thickness. The thickness of the deposit 10 on the edge portions 12 of the teeth adjacent the points may be from about 0.005 to about 0.020 or more and may taper to a less thickness towards the base of the teeth. The thickness adjacent the points coupled with the firm support obtained through the cooperation with the deposits 10 of the film 18 and the fibrous material resist crushing or deformation under the stresses developed in tearing of sheet material which have blunted or deformed previous stiffened serrations of fibrous cartons.

Resinous materials for deposit on marginal face portions and teeth edge portions of a fibrous sheet 16 are those readily fusible to a molten fluid having a viscosity suitable for application in the desired relation and solidifying rapidly on cooling to a strong tough condition. Resins having a viscosity in molten condition of preferably at least about 20,000 cps. as determined at 225 C. with a Brookfield Viscometer using a No. 4 spindle and speed of r.p.m. have been useful using a smooth surfaced applicator and conventional fibrous material carton blanks; but somewhat lower or higher viscosity materials may be used. Excellent tearing edges have been obtained with resinous material having in cooled and hardened condition a hardness in excess of 25 on the Shore D scale and a tensile strength preferably of about 3,000- lbs. per square inch and higher.

Resins having these characteristics include relatively high molecular weight polyesters from reaction of one or more dicarboxylic acids such as terephthalic acid and isophthalic acid with lower alkylene gylcols such as ethylene glycol or butylene glycol, polyesteramides, for example, adipic polyesteramides in which the hydroxy component is 1,6 hexane diol, 1,4 butane diol or ethylene glycol, and polyamide resins such as the nylon materials and polyamides from condensation of dimerized oleic acid and ethylene diamine or polyalkylene polyamines. Preferred resinous polyesters include condensates of a lower alkylene gylcol for example, 1,4 butane diol with mixed terephthalic and isophthalic acid components with the acid components in the molar ratio of from about 1:1 to about 4:1. These preferred polyesters will be condensed to provide melting points of from about 80 to about 200 C.

Deposition of relatively thick deposits 10 of resinous material along the edges of the teeth and a relatively thin film 18 along the face 10 of the fibrous sheet may be effected by pressing marginal portions along the serrated edge of a face 20 of the sheet 16 into a layer 22 of molten adhesive on a hot surface 24. In general, the molten layer 22 may be from about A; to about A the thickness of the fibrous sheet, preferably from 0.002 to 0.010" in thickness. The exact thickness to be used depends upon the thickness of the sheet material 16 on which the material is to be deposited and on the amount of resin which it is desired to deposit. Depositing the material from such a supported layer 22 of resin rather than from a molten body of substantial thickness or from a nozzle i important since the action involved is, at least in part, squeezing of the molten material from between the surface 20 of the fibrous sheet 16 and the carrier film 18 along the face 20 of the fibrous sheet may be surface 24 on which the layer 22 of molten resin is supplied. The squeezed-out material rises above the level of the adhesive layer 22 so that it can wet and form relatively thick deposits 10 on the edge portions 12 of the teeth 14. Also this enables control of the thickness of the unifying and reinforcing film 18 on the face portions of the sheet material while at the same time providing substantial deposits 10 of material on the tooth edge portions 12.

Although other apparatus may be used, a hot melt applicator 30 similar to that shown in the patent to Paulsen 2,726,629 of Dec. 13, 1955, has been found useful. In this device solid thermoplastic resin material in the form of a red 32 is fed through a channel 34 into a heated chamber 36 in which is mounted a disk or wheel of which the circumferential surface 24 serves as a carrier surface for the resin layer 22 and defines, with the walls of the chamber 36, a passageway 42 in which the thermoplastic material is melted and spread on the surface 24 of the wheel 38. As shown in FIGS. 3 and 4, the marginal portions of the face 20 of the fibrous sheet 16 are pressed into contact with the layer 22 of adhesive on the wheel 38 by a guide wheel 46 disposed to press against the fibrous sheet 16 along a line spaced slightly inward of the bottoms of the teeth 14.

It is preferred that the direction of feed of the fibrous sheet 16 be counter to the direction of movement of the surface 24 of the disk or wheel 38 at the point of contact as shown in FIG. in order that the applicator wheel 38 may wipe on a smooth film 18 of molten material in wetting engagement on the surface 20 of the sheet material. In this procedure the edge portions 12 of the teeth 14 on the side of the teeth in which the sheet material is moving plow up molten material from the layer 22 on the surface 24 of the disk or wheel, and the plowed-up material is deposited primarily on these edge portions. It will be noted that the edge portions 12 adjacent the points of the teeth 24 collect the molten material deposited by the same linear distance of movement of the wheel as do the edge portions 12 adjacent the bottoms of the teeth. Since the molten material on the surface 24 of the wheel adjacent the points is not consumed by deposition on significant areas of the face 20 of the sheet material 16, there is available and is collected by the edge portions near the points a greater quantity of molten material than i collected near the bottoms of the teeth. This greater quantity of material provides a thicker and stronger cross section adjacent the points where it is needed to initiate tearing than is deposited adjacent the bottoms of the teeth. Also since, as shown in FIG. 5, the material is deposited primarily on only one edge of each tooth a strong thick edge is obtained with less material. After deposition of the molten material on the blank, the molten material quickly cools and hardens to form the desired reinforced tooth structure.

Although it is preferred to use a direction of feed of the sheet material 16 counter to that of the movement of the surface 24 carrying the molten layer 44, it is possible to operate as shown in FIG. 6 with the carrier surface 24 moving in the same direction as the sheet material 16. With this mode of operation, deposition of molten material occurs due to the displacement of molten material of the layer when face portions 20 of the sheet material 16 are pressed towards the carrier surface. This displaced material flows up and above the general level of molten material on the surface and deposits on both edges 12 of the teeth 14 as shown in FIGS. 6 and 7. It is to be noted that in this operation it has been found generally preferable to use a somewhat thicker layer of molten material on the carrier surface such as the surface of an applicator wheel. Also, although the same greater deposition adjacent the points of the teeth is not secured in this procedure as was obtained in the procedure noted above, using counter movement, nevertheless, since the material deposits on both edges of the teeth it has been found to provide adequate tooth reinforcement. However, the operation is less desirable from certain points of view such as its normal requirement of a higher quantity of material to achieve the same reinforcement as obtained with a counter movement and some difficulties in maintaining uniformity of deposition.

By way of illustration and not by way of limitation, there has been used a resinous polyester formed by condensation and polymerization of 4 mols of terephthalic acid and 1 mol of isophthalic acid with 1,4 butane diol and having a melting point of 190 C., a Shore D hardness of about 75, a tensile strength of 3000 pounds per square inch and a viscosity at 225 C. of 70,000 cps. (Brookfield Viscometer using #4 spindle at r.p.m.). This material was deposited on the serrated marginal edge portions of a carton blank of 0.015 inch thick cardboard with A inch high teeth by an applicator wheel having a circumference of one foot rotating in a reverse direction to that of the movement of the sheet material. An 0.006 thickness of molten resin material at a temperature of 430 F. on the applicator surface was effective to deposit a film of from .006 to .007" thickness on the face of the sheet material using a 500 foot per minute rate of feed for the sheet material and a reverse circumferential speed of 500 feet per minute of the applicator Wheel. In this operation the resin deposits on the edges of the teeth ranged up to about .010" in thickness.

In an alternative procedure using the same conditions and materials as above but operating with the surface speed of the applicator wheel at 500 feet per minute in the same direction as the sheet material feed and with a 500 foot per minute rate of feed of the sheet material, there was obtained a deposit of about 0.004" thickness of resin on the face of the sheet material and a thickness at the points of the teeth approximating 0.006 inch. While the reinforcement was satisfactory in operation, the film was much more irregular and there was some tendency to the formation of fine threads of material extending between the points of adjoining teeth.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. The method of forming a tearing edge for severing paper and the like which comprises providing a fibrous sheet formed with serrations along an edge, pressing a marginal portion of one face of said sheet in a band extending from the serrated edge of the sheet to an area below the base of the serrations into a layer of molten thermoplastic material on a carrier surface, said layer of adhesive extending from areas beneath said face to areas beyond said serrated edge, said pressing operating to displace portions of said layer from between said sheet and said carrier surface and cause said portions to flow to a level above the free surface of said layer into wetting engagement with edge surfaces of the serrations, said layer being from A; to the thickness of said sheet, removing said face portion from said layer with molten thermoplastic material thereon including portions on the face of said sheet below the base of the serrations and other portions covering edge surfaces and ends of the serrations, and cooling said thermoplastic material on said sheet to solidify it to a hard body including hardened edge surfaces and ends on the serrations and hardened material on the face of the sheet supporting the hardened resin on the edges and ends of the serrations against stresses encountered in tearing sheet material against the serrations.

2. The method of forming a tearing edge for severing paper and the like which comprises providing a fibrous sheet formed with serrations at least inch in height along an edge, pressing successive marginal portions of one face of said sheet in a band extending from the serrated edge of the sheet to at least A inch below the base of the serrations into a layer of molten thermoplastic material on a carrier surface, said layer of adhesive extending from areas beneath said face to areas beyond said serrated edge, said pressing operating to displace portions of said layer from between said sheet and said carrier surface and cause said portions to flow to a level above the free surface of said layer into wetting engagement with edge surfaces of the serrations, said layer being from A3 to the thickness of said sheet, removing successive marginal face portions from said layer with rnolten thermoplastic material thereon including portions on the face of said sheet below the base of the serrations and other portions covering edge surfaces and ends of the serrations, and cooling said thermoplastic material on said sheet to solidify it to a hard body including hardened edge surfaces and ends on the serrations and hardened material on the face of the sheet supporting the hardened resin on the edges and ends of the serrations against stresses encountered in tearing sheet material against the serrations.

3. The method of forming a tean'ng edge for severing paper and the like which comprises providing a fibrous sheet formed with serrations at least inch in height along an edge, pressing successive marginal portions of one face of said sheet in a band extending from the serrated edge of the sheet to at least 5 inch below the base of the serrations into successive portions of a layer of molten thermoplastic material on a carrier surface moving relative to said sheet in a direction generally parallel to said edge, said layer of adhesive extending from areas beneath said face to areas beyond said serrated edge, said pressing operating to displace portions of said layer from between said sheet and said carrier surface and cause said portions to flow to a level above the free surface of said layer into wetting engagement with edge surfaces of the serrations, said layer being from A; to the thickness of said sheet, removing successive marginal face portions from. said layer with molten thermoplastic material thereon including relatively thin portions on the face of said sheet below the base of the serrations and other thicker portions covering edge surfaces and ends of the serrations, and cooling said thermoplastic material on said sheet to solidify it to a hard body including hardened edge surfaces and ends on the serrations and hardened material on the face of the sheet supporting the hardened resin on the edges and ends of the serrations against stresses encountered in tearing sheet material against the serrations.

4. The method of forming a tearing edge for severing paper and the like which comprises providing a cardboard sheet formed with serrations at least inch in height along an edge, pressing successive marginal portions of one face of said sheet in a band extending from the serrated edge of the sheet to at least ,4 inch below the base of the serrations into successive portions of a layer of molten thermoplastic material on a carrier surface moving relative to said sheet in a direction generally parallel to said edge, said layer of adhesive extending from areas beneath said face to areas beyond said serrated edge, said pressing operating to displace portions of said layer from between said sheet and said carrier surface and cause said portions to flow to a level above the free surface of said layer into wetting engagement with edge surfaces of the serrations, said thermoplastic material having a viscosity of at least about 20,000 centipoises in said molten condition, said layer being from /s to A: the thickness of said sheet, removing successive marginal face portions from said layer with molten thermoplastic material thereon including relatively thin portions on the face of said sheet below the base of the serrations and other thicker portions covering edge surfaces and ends of the serrations, and cooling said thermoplastic material on said sheet to solidify it to a hard body including hardened edge surfaces and ends on the serrations and hardened material on the face of the sheet supporting the hardened resin on the edges and ends of the serrations against stresses encountered in tearing sheet material against the serrations.

References Cited UNITED STATES PATENTS 395,645 1/1889 Anderson 117-111 1,887,912 11/1932 Begle 225-49 1,952,431 3/ 1934 Gluck et al. 225-91 X 2,311,587 2/1943 Vaala 260-33 2,319,307 5/1943 Eddy 117-4 X 2,633,985 4/ 1953 Meyer 225-48 X 2,659,340 11/1953 Zinn 118-202 2,726,629 12/ 1955 Paulsen 117-43 3,136,650 6/1964 Avila 117-21 3,137,424 6/ 1964 Finn et a1. 225-48 WILLIAM D. MARTIN, Primary Examiner. W. D. HERRICK, Assistant Examiner. 

1. THE METHOD OF FORMING A TEARING EDGE FOR SEVERING PAPER AND THE LIKE WHICH COMPRISES PROVIDING A FIBROUS SHEET FORMED WITH SERRATIONS ALONG AN EDGE, PRESSING A MARGINAL PORTION OF ONE FACE OF SAID SHEET IN A HAND EXTENDING FROM THE SERRATED EDGE OF THE SHEET TO AN AREA BELOW THE BASE OF THE SERRATIONS INTO A LAYER OF MOLTEN THERMOPLASTIC MATERIAL ON A CARRIER SURFACE, SAID LAYER OF ADHESIVE EXTENDING FROM AREAS BENEATH SAID FACE TO AREAS BEYOND SAID SERRATED EDGE, SAID PRESSING OPERATING TO DISPLACE PORTIONS OF SAID LAYER FROM BETWEEN SAID SHEET AND SAID CARRIER SURFACE AND CAUSE SAID PORTIONS TO FLOW TO A LEVEL ABOVE THE FREE SURFACE OF SAID LAYER INTO WETTING ENGAGEMENT WITH EDGE SURFACES OF THE SERRATIONS, SAID LAYER BEING FROM 1/8 TO 3/4 THE THICKNESS OF SAID SHEET, REMOVING SAID FACE PORTION FROM SAID LAYER WITH MOLTEN THERMOPLASTIC MATERIAL THEREON INCLUDING PORTIONS ON THE FACE OF SAID SHEET BELOW THE BASE OF THE SERRATIONS AND OTHER PORTIONS COVERING EDGE SURFACES AND ENDS OF THE SERRATIONS, AND COOLING SAID THERMOPLASTIC MATERIAL ON SAID SHEET TO SOLIDIFY IT TO A HARD BODY INCLUDING HARDENED EDGE SURFACES AND ENDS ON THE SERRATIONS AND HARDENED MATERIAL ON THE FACE OF THE SHEET SUPPORTING THE HARDENED RESIN ON THE EDGES AND ENDS OF THE SERRATIONS AGAINST STRESSES ENCOUNTERED IN TEARING SHEET MATERIAL AGAINST THE SERRATIONS. 